Catcher's Knee: Posterior Femoral Condyle Juvenile Osteochondritis

ORIGINAL ARTICLE

Catcher’s Knee: Posterior Femoral Condyle Juvenile Osteochondritis Dissecans in Children and Adolescents Mark J. McElroy, MS,* Patrick M. Riley, MD,w Frances A. Tepolt, MD,w Adam Y. Nasreddine, MA,w and Mininder S. Kocher, MD, MPH*w

(J Pediatr Orthop 2016;00:000–000) Background: Juvenile osteochondritis dissecans is an idiopathic condition involving subchondral bone and articular cartilage in skeletally immature patients in whom the growth plates are steochondritis dissecans (OCD) of the knee is a lo- open, potentially leading to lesion instability. Because of the Ocalized pathologic process in which an area of sub- differing forces experienced by baseball/softball catchers versus chondral bone undergoes metabolic changes or position players, the age at which lesions develop and the diminished blood supply, potentially involving separation characteristics of the lesions themselves may differ between these of the bone and overlying cartilage from surrounding 2 populations. The purpose of the study was to examine relative bony tissue.1 Despite the condition first being described age and characteristics of osteochondritis dissecans (OCD) knee over 100 years ago by Paget2 and Konig,3 its precise eti- lesions in catchers compared with position players. ology and natural history remain largely speculative and Methods: Using a text-based search tool that queries clinic notes controversial. Ischemia, repetitive trauma, abnormal os- and operative reports, computerized medical records from 1990 sification, genetics, and inflammation have all been to 2014 from the Sports Medicine Program of a tertiary care postulated as etiological factors.4–8 Recent increased Children’s Hospital were searched to find children and adoles- participation and specialization in youth sports and the cents who had OCD of the knee, played baseball/softball, had a rising rate of OCD in skeletally immature athletes may specified field position, and had magnetic resonance imaging of support the theory of overuse and repetitive micro- the knee. Ultimately, 98 knees (78 patients) were identified: 33 trauma,9,10 with OCD recently being reported as the knees (29 patients) in catchers and 65 knees (49 patients) in fourth most common overall injury in young athletes seen noncatchers. Data collected included position played (catcher/ at a large pediatric hospital.11,12 Incidence in the general noncatcher), demographics (age, unilateral/bilateral, and sex), population has been reported to be <30/100,000.13,14 lesion severity, and sagittal and coronal lesion location. OCD has been classified as juvenile OCD (jOCD) if Results: When compared with noncatchers, catchers presented the growth plates are open and adult OCD if the growth at a younger age (P = 0.035) but were similar with respect to plates are closed.15 OCD has further been classified based bilateral involvement (P=0.115), sex (P=0.457), and lesion on location and stability, with the lateral aspect of the severity (P=0.484). Lesions in catchers were more posterior on medial femoral condyle being the most common loca- the femoral condyle in the sagittal plane (P=0.004) but similar tion.6,16–18 Both nonoperative10,19 and operative20–25 in location in the coronal plane (P=0.210). treatments have been described. Nonoperative treatment is Conclusions: Catchers developed OCD at a younger age and in a usually recommended for stable jOCD lesions with intact more posterior location on the medial and lateral femoral con- articular cartilage and typically consists of activity re- dyles than noncatchers. These results may represent the effects striction. Operative treatment is usually recommended for of repetitive and persistent loading of the knees in the hyper- adult OCD lesions, unstable lesions, and stable lesions that flexed position required of catchers. Increased awareness of this have failed nonoperative treatment. Surgical treatment risk may lead to surveillance and prevention programs. options include drilling, fixation, and chondral resurfacing. Level of Evidence: Level III—case-control study. Attention has been paid to overuse upper extremity Key Words: OCD, osteochondritis dissecans, baseball, softball, injuries in youth baseball and softball players including catcher, microtrauma Little League Shoulder, Little League Elbow, internal impingement of the shoulder, OCD of the capitellum, medial epicondyle apophyseal injuries, and ulnar collat- eral ligament injuries. Early detection of injuries and the From the *Harvard Medical School; and wDepartment of Orthopaedic Surgery, Boston Children’s Hospital, Boston, MA. establishment of pitch count regulations can reduce the 26–28 None of the authors received any external financial support. number of these injuries. However, little attention The authors declare no conflicts of interest. has been paid to overuse injuries of the lower extremity in Reprints: Mininder S. Kocher, MD, MPH, Department of Orthopaedic these athletes. In particular, the repetitive and persistent Surgery, Boston Children’s Hospital, 300 Longwood Avenue, Hunnewell 2, Boston, MA 02115. E-mail: mininder.kocher@ knee hyperflexion required to play baseball/softball childrens.harvard.edu. catcher may influence the development and characteristics Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved. of OCD lesions.

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FIGURE 1. Cohort selection. MRI indicates magnetic resonance imaging; OCD, osteochondritis dissecans.

The purpose of this study was to describe the age of METHODS presentation and characteristics of OCD lesions of the knee in youth baseball and softball players and to de- Patient Population termine if these parameters diﬀered between catchers and Inclusion criteria for the study were: children and position players. adolescents 18 years old or younger, OCD of the knee,

TABLE 1. Hefti Staging Scale for Osteochondritis Dissecans TABLE 2. Patient Characteristics Grouped by Catcher and Stage Description Noncatcher Position Metric Catchers Noncatchers P I Small change of signal without clear margins of fragment II Osteochondral fragment with clear margins but without ﬂuid No. Patients (involved knees) 29 (33) 49 (65) between fragment and underlying bone Age (average ± SD) (y) 12.7 ± 2.0 13.7 ± 2.3 0.035 III Fluid is visible partially between fragment and underlying bone Laterality 4 bilateral 16 bilateral 0.115 IV Fluid is completely surrounding the fragment, but the fragment is 25 unilateral 33 unilateral still in situ Sex 25 M 45 M 0.457 V Fragment is completely detached and displaced (loose body) 4F 4F

F indicates female; M, male. played baseball and/or softball at the time he/she pre- teochondritis dissecans” OR “ICD9 732.9 Unspecified sented with OCD, the position the patient played was osteochondropathy”). specified in the medical record, and magnetic resonance The final cohort consisted of 98 knees in 78 patients. imaging (MRI) of the affected knee was available. There were 33 knees in 29 catchers and 65 knees in 49 A computerized search was performed of the med- noncatchers. Only 6 of the 29 catchers reported playing ical records of a large tertiary care Children’s Hospital other positions in addition to catcher. from 1990 to 2014 using a text-based tool that queries clinical notes and operative reports. A detailed review of the records returned by the search was then performed to confirm that each patient met the inclusion criteria. The Measurements/Definitions results of this search and filtering process are shown Demographics in Figure 1. The original query was performed with the Demographics of the catcher and noncatcher following broad search string to maximize patient iden- groups were compared, including age at MRI imaging of tification: (“baseball” OR “softball”) AND (“OCD” OR the lesion, whether the patient had unilateral versus bi- “jOCD” OR “osteochondritis” OR “ICD-9 732.7 Os- lateral lesions, and sex.

Lesion Severity The severity of each lesion was determined using 2 methods. First, a pediatric orthopaedic sports medicine fellow read T2-weighted MRIs to evaluate fluid within the lesion and T1-weighted MRIs to evaluate breaks in the articular cartilage. Each lesion was then graded using the Hefti staging scale,6 which defines the 5 stages outlined in Table 1. Second, for patients who required surgical treatment, the stage determined using the MRI was con- firmed by narrative accounts of the lesion from the pediatric orthopaedic sports medicine attending surgeon’s operative report. When disagreement existed between the fellow’s MRI read and the attending surgeon’s report, a second attending was consulted to read the MRI.

FIGURE 2. Cahill and Berg classification system used for lesion location stratification. Regions are defined as follows: coronal plane (A) region 1—medial portion of medial femoral condyle; region 2—lateral portion of medial femoral condyle; region 3—between walls of intercondylar tunnel; region 4—medial portion of lateral femoral condyle; region 5—lateral portion of lateral femoral condyle; patella. Sagittal plane (B) region A— anterior to region B; region B—anterior border formed by line projecting along roof of intercondylar tunnel; posterior border formed by line projecting distally from and parallel to posterior femoral cortex; region C—posterior to region B; patella. FIGURE 3. Hefti stage of lesions divided by player position.

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Lesion Location Sagittal Location Of 33 knees in catchers, 15 had OCD in location C and 9 had OCD in location B. Of 65 knees in noncatchers, 12 had OCD in location C and 39 had OCD in location B. There was statistical signiﬁcance in the following comparisons: overall distribution of sagittal locations was diﬀerent between catchers and noncatchers (P=0.012), lesions in catchers were more likely to be in region C than lesions in noncatchers (P=0.010), and lesions in noncatchers were more likely to be in region B than lesions in catchers (P=0.004) (Fig. 4).

Coronal Location Neither the overall distribution of coronal locations nor any of the individual regions were significantly dif- ferent between catchers and noncatchers (P=0.210) (Figs. 5–7). FIGURE 4. Sagittal location of lesions divided by player position. DISCUSSION With increased specializationinyouthsportsandyear Lesion Location round play, the risk of injury has increased. Overuse upper The location of each lesion was determined using extremity injuries in youth baseball and softball players, the Cahill and Berg classification system, which defines 3 including Little League Shoulder and Little League Elbow, regions based on the sagittal perspective and 5 regions have received increasing attention. Early detection of these 29 based on the coronal perspective. For the purposes of injuries may result in successful healing with nonoperative statistical comparisons in the current study, patellar le- treatment.30 Prevention of these injuries may occur by using sions were added to the original Cahill and Berg system as pitch counts and decreasing exposure. However, to date, a fourth sagittal category and sixth coronal category. The overuse injuries of the lower extremity in youth baseball and final system used in the current study is detailed softball players have not garnered equal attention. In this in Figure 2. study, we describe “Catcher’s Knee,” which is a posterior femoral condylar OCD lesion seen with the repetitive and Statistical Analyses persistent hyperflexion seen in catchers. Ages between the catcher and noncatcher cohorts In this cohort from a tertiary care children’s hos- were compared using 2-tailed Student t test. All other pital, catchers presented with OCD at a younger age than comparisons were performed using w2 or Fisher exact test position players, possibly reflecting the trend of younger where appropriate. The level of significance was set at positional specialization. Lesion severity did not differ P=0.05. between the 2 groups, which may indicate the chronic rather than acute nature of the condition or that patients Funding and Institutional Review Board Approval No funding was received for the completion of this study. Institutional review board approval was obtained.

RESULTS Demographics When compared with the cohort of noncatchers, the cohort of catchers presented at a younger age (P=0.035) but had similar distributions of unilateral versus bilateral lesions (P=0.115) and male versus female patients (P=0.457) (Table 2).

Lesion Severity Neither the overall distribution of Hefti staging nor any of the individual stages were signiﬁcantly diﬀerent FIGURE 5. Coronal location of lesions divided by player po- between catchers and noncatchers (P=0.484) (Fig. 3). sition.

Copyright r 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. J Pediatr Orthop Volume 00, Number 00, ’’ 2016 Catcher’s Knee OCD in Children and Adolescents simply present at a similar level of discomfort regardless The higher percentage of medial femoral condyles in of how or when the injury begins. OCD lesions in the current cohort is in agreement with the location found catchers were more posterior than position players. This in past reports of the general population. The 55% and difference may occur because of repetitive and persistent 66% medial lesions in catchers and noncatchers (exclud- hyperflexion of the knee in catchers compared with the ing patellar lesions), respectively, roughly coincide with upright loading in position players (Fig. 8). Coronal le- the 64% to 87%6,10,13,31–33 of medial locations found in sion location did not differ between catchers and non- the literature. It is possible that the trend toward a lower catchers, possibly reflecting that squatting does not alter portion of medial lesions in catchers reflects the valgus the force distribution as much in the coronal plan as in position that many catchers adopt when in a deep squat, the sagittal plane. placing higher stress on the lateral femoral condyle.

FIGURE 6. Sagittal magnetic resonance imaging (A), sagittal radiograph (B), coronal magnetic resonance imaging (C), and notch view radiograph (D) of osteochondral dissecans lesion on posterior lateral femoral condyle of 12.8-year old male baseball catcher. Posterior (regionC)locationwassignificantlymorecommonincatchersthan noncatchers. The white box identifies the lesion location.

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FIGURE 7. Sagittal magnetic resonance imaging (A), sagittal radiograph (B), coronal magnetic resonance imaging (C), and coronal radiograph (D) of osteochondral dissecans lesion on medial femoral condyle of 14.8-year old male baseball pitcher and second baseman. Upright weight-bearing (region B) location was significantly more common in noncatchers than catchers. The white box identifies the lesion location.

This study had several limitations. First, 6 of the 29 being retrospectively examined would have influenced catchers also reported playing other positions, including whether a position was recorded, so the final cohort is likely pitcher, first base, second base, shortstop, third base, and a representative subset of the population. Third, many outfield. This number of players is likely small enough to young athletes play several sports. Although this diversity not skew the findings. Second, a portion of the original precludes isolating catcher statusastheonlypredictorvar- search results were eliminated because the records did not iable, participation in other high risk sports or positions is specify a position played. It is unlikely that the parameters likely spread evenly across both the catcher and noncatcher

FIGURE 8. Weight-bearing region in upright position typical of noncatchers (A) versus posterior weight-bearing region typical of catcher’s squat (B). cohorts in a way that minimizes confounding effects. For regarding age appropriate adoption of pitch types may instance, it is unlikely that all catchers are also at high risk reduce injury. Similarly, prevention of Catcher’s Knee may due to being football centers whereas all noncatchers are at be influenced by “catch counts” and equipment such as low risk due to being basketball point guards. Lastly, de- triangular foam “knee savers” that are placed behind the termining the severity and location of OCD lesions by knee to reduce knee flexion or unload the knee in hyper- imaging and even intraoperatively can be difficult and is flexion. However, more research is needed to assess the often not completely reliable. efficacy of these prevention strategies. OCD of the knee is a serious condition that can require surgical treatment and increases the risk of os- teoarthritis.1 If detected in early stages, OCD can be REFERENCES 1. Heyworth BE, Kocher MS. Osteochondritis dissecans of the knee. treated nonoperatively with relatively high healing rates, JBJS Reviews. 2015;3:e1. excellent function, and minimal risk of long-term seque- 2. Paget J. On the production of some of the loose bodies and joints. St lae. If detected later, OCD may require aggressive surgical Bartholomew’s Hosp Rep. 1870;6:1–4. treatment including surgical fixation, bone grafting, and 3. Konig F. Ueber freie korper in den geleken [On loose bodies in the joint]. Dtsch Z Chir. 1887-1888;27:90. chondral resurfacing. Thus, characterizing the risks of 4. Clanton TO, DeLee JC. Osteochondritis dissecans. History, certain activities, such as playing catcher, is helpful in that pathophysiology and current treatment concepts. Clin Orthop Relat it aids in developing programs to address unique ex- Res. 1982;167:50–64. posures and minimize late detection. 5. Flynn JM, Kocher MS, Ganley TJ. Osteochondritis dissecans of the Prevention of youth sports injuries has been empha- knee. J Pediatr Orthop. 2004;24:434–443. 6. Hefti F, Beguiristain J, Krauspe R, et al. Osteochondritis dissecans: sized. For upper extremity injuries in youth baseball and a multicenter study of the European Pediatric Orthopedic Society. softball, pitch counts, technique, and recommendations J Pediatr Orthop B. 1999;8:231–245.

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